Spatial Mapping for a Visual Prosthesis

ABSTRACT

A visual prosthesis and a method of operating a visual prosthesis are disclosed. Neural stimulation through electrodes is controlled by spatial maps, where a grouped or random association is established between the data points of the acquired data and the electrodes. In this way distortions from the foveal pit and wiring mistakes in the implant can be corrected. Moreover, broken electrodes can be bypassed and a resolution limit can be tested, together with testing the benefit the patient receives from correct spatial mapping.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 12/114,657, filed May 2, 2008, for “Spatial Mapping for aVisual Prosthesis” which claims priority to U.S. Provisional Application60/928,407 filed on May 8, 2007 and U.S. Provisional Application60/928,440 filed on May 8, 2007, the contents of both of which areincorporated herein by reference in their entirety. This application mayalso be related to U.S. application Ser. No. 12/114,557, filed May 2,2008, for “Method And System For Providing Stimulation Inputs To AVisual Prosthesis Implant” the contents of which are also incorporatedby reference in their entirety.

STATEMENT OF GOVERNMENT INTEREST

This invention was made with government support under grant No.R24EY12893-01, awarded by the National Institutes of Health. Thegovernment has certain rights in the invention.

FIELD

The present disclosure relates to operation of visual prosthesesimplants. More in particular, it relates to a spatial mapping for avisual prosthesis.

SUMMARY

According to a first aspect, a method of mapping relationship of pixelsof an acquired image to electrodes of a visual prosthesis implantadapted to be positioned on the retina of a subject is provided, themethod comprising: associating a plurality of pixels of the acquiredimage to form a group of pixels; associating a plurality of electrodesto form a group of electrodes; and mapping the group of pixels to thegroup of electrodes.

According to a second aspect, a visual prosthesis is provided,comprising: an implanted portion having a radiofrequency receiver and anarray of electrodes suitable for stimulating visual neurons; and anexternal portion having a video processing unit and including a spatialredirection map, wherein the spatial redirection map establishes arelationship between an image acquired by the visual prosthesis and thearray of electrodes, the relationship providing an association betweenan average pixel value of a plurality of pixels and a subset of thearray of electrodes.

According to a third aspect, a method of mapping relationship of pixelsof an acquired image to electrodes of a visual prosthesis implantadapted to be positioned on the retina of a subject is provided, themethod comprising: dividing the acquired image in a plurality of areas,positioning the electrodes on the retina in a way that a one-to-onespatial relationship between each area and each electrode is implicitlyestablished; and mapping each area to each pixel in a random one-to-onespatial relationship different from the implicitly establishedone-to-one spatial relationship.

According to a fourth aspect, a visual prosthesis is provided,comprising: an implanted portion having a radiofrequency receiver and anarray of electrodes suitable for stimulating visual neurons; and anexternal portion having a video processing unit and including a spatialredirection map, wherein the spatial redirection map establishes arelationship between an image acquired by the visual prosthesis and thearray of electrodes, the relationship providing a random associationbetween each pixel value and each electrode of the array of electrodes.

Further embodiments of the present disclosure can be found in thewritten specification, drawings and claims of the present application.

Therefore, the present disclosure provides a flexible and arbitrarymapping between the input video image and the stimulation electrodes tocorrect distortions from the foveal pit, correct wiring mistakes in theimplant, bypass broken electrodes using current summation to enablenon-sensitive electrodes, test the resolution limit of the implant, testthe benefit the patient receives from correct spatial mapping, and tosolve orientation problems of the array on the retina.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1 and 2 show a retinal stimulation system

FIG. 3 shows components of a fitting system.

FIG. 4 is a diagram of a standard electrode mapping as known in theprior art.

FIG. 5 is a diagram of an electrode mapping in accordance with a firstembodiment of the present disclosure.

FIG. 6 is a diagram of an electrode mapping in accordance with a secondembodiment of the present disclosure.

DETAILED DESCRIPTION

A Retinal Stimulation System, disclosed in U.S. application Ser. No.11/207,644, filed Aug. 19, 2005 for “Flexible Circuit Electrode Array”by Robert J. Greenberg, et, al. incorporated herein by reference, isintended for use in subjects with retinitis pigmentosa. FIG. 1 and FIG.2 show a Retinal Stimulation System (1) wherein a patient/subject isimplanted with a visual prosthesis. Reference can also be made to FIGS.1-5 of U.S. application Ser. No. 11/796,425, filed Apr. 27, 2007 for“Visual Prosthesis Fitting”, also incorporated herein by reference inits entirety.

The Retinal Stimulation System (1) is an implantable electronic devicecontaining electrode array (2) that is electrically coupled by a cable(3) that pierces sclera of the subject's eye and is electrically coupledto an electronics package (4), external to the sclera. The RetinalStimulation System (1) is designed to elicit visual percepts in blindsubjects with retinitis pigmentosa.

Referring to FIG. 3, a Fitting System (FS) may be used to configure andoptimize the visual prosthesis (3) of the Retinal Stimulation System(1).

The Fitting System may comprise custom software with a graphical userinterface (GUI) running on a dedicated laptop computer (10). Within theFitting System are modules for performing diagnostic checks of theimplant, loading and executing video configuration files, viewingelectrode voltage waveforms, and aiding in conducting psychophysicalexperiments. A video module can be used to download a videoconfiguration file to a Video Processing Unit (VPU) (20) and store it innon-volatile memory to control various aspects of video configuration,e.g. the spatial relationship between the video input and theelectrodes, which is one of the main aspects of the present disclosure.The software can also load a previously used video configuration filefrom the VPU (20) for adjustment.

The Fitting System can be connected to the Psychophysical Test System(PTS), located for example on a dedicated laptop (30), in order to runpsychophysical experiments. In psychophysics mode, the Fitting Systemenables individual electrode control, permitting clinicians to constructtest stimuli with control over current amplitude, pulse-width, andfrequency of the stimulation. In addition, the psychophysics moduleallows the clinician to record subject responses. The PTS may include acollection of standard psychophysics experiments developed using forexample MATLAB (MathWorks) software and other tools to allow theclinicians to develop customized psychophysics experiment scripts.

Any time stimulation is sent to the VPU (20), the stimulation parametersare checked to ensure that maximum charge per phase limits, chargebalance, and power limitations are met before the test stimuli are sentto the VPU (20) to make certain that stimulation is safe.

Using the psychophysics module, important perceptual parameters such asperceptual threshold, maximum comfort level, and spatial location ofpercepts may be reliably measured.

Based on these perceptual parameters, the fitting software enablescustom configuration of the transformation between video image andspatio-temporal electrode stimulation parameters in an effort tooptimize the effectiveness of the retinal prosthesis for each subject.

The Fitting System laptop (10) is connected to the VPU (20) using anoptically isolated serial connection adapter (40). Because it isoptically isolated, the serial connection adapter (40) assures that noelectric leakage current can flow from the Fitting System laptop (10).

As shown in FIG. 3, the following components may be used with theFitting System according to the present disclosure. A Video ProcessingUnit (VPU) (20) for the subject being tested, a Charged Battery (25) forVPU (20), Glasses (5), a Fitting System (FS) Laptop (10), aPsychophysical Test System (PTS) Laptop (30), a PTS CD (not shown), aCommunication Adapter (CA) (40), a USB Drive (Security) (not shown), aUSB Drive (Transfer) (not shown), a USB Drive (Video Settings) (notshown), a Patient Input Device (RF Tablet) (50), a further Patient InputDevice (Jog Dial) (55), Glasses Cable (15), CA-VPU Cable (70), CFS-CACable (45), CFS-PTS Cable (46), Four (4) Port USB Hub (47), Mouse (60),LED Test Array (80), Archival USB Drive (49), an Isolation Transformer(not shown), adapter cables (not shown), and an External Monitor (notshown).

The external components of a Fitting System may be configured asfollows. The battery (25) is connected with the VPU (20). The PTS Laptop(30) is connected to FS Laptop (10) using the CFS-PTS Cable (46). ThePTS Laptop (30) and FS Laptop (10) are plugged into the IsolationTransformer (not shown) using the Adapter Cables (not shown). TheIsolation Transformer is plugged into the wall outlet. The four (4) PortUSB Hub (47) is connected to the FS laptop (10) at the USB port. Themouse (60) and the two Patient Input Devices (50) and (55) are connectedto four (4) Port USB Hubs (47). The FS laptop (10) is connected to theCommunication Adapter (CA) (40) using the CFS-CA Cable (45). The CA (40)is connected to the VPU (20) using the CA-VPU Cable (70). The Glasses(5) are connected to the VPU (20) using the Glasses Cable (15).

In a visual prosthesis, every electrode in the implanted array ofelectrodes produces a spot of light (phosphene) in the visual field. Atransformation needs to be specified to map the stimulation ofindividual electrodes in the stimulating array to specific locations, orregions, in the acquired video image. This transformation is specifiedin a look-up table referred to as the spatial map. In other words,spatial mapping is the relationship of a pixel, or pixels, in thecamera's view to an electrode on the retina. Due to the optics of theeye, the retina is laid out reverse of the real world and proportional.The scale depends on the distance of the object.

As shown in the prior art embodiment of FIG. 4, usually a one-to-onespatial mapping is used. In this mapping, the locations of theindividual electrodes in the retinal stimulating array are projectedinto the visual field. The corresponding locations of the input videoimage (pixels) are then mapped to the corresponding single electrode inthe array. FIG. 4 shows a 4×4 prior art electrode array embodiment,where pixel (80) is mapped to electrode L6, pixel (90) is mapped toelectrode L7, pixel (100) is mapped to electrode M4, pixel (110) ismapped to electrode M1, and so on, so that each pixel corresponds to asingle electrode and vice versa. In other words, the correspondinglocations of the input video image (pixels) are mapped to thecorresponding single electrode in the array.

However, in certain cases there is a need to use a different mapping.For example, a regular spacing of stimulating electrodes may result in adistorted spatial pattern of phosphenes. Because the ganglion cell axonsare stretched away from their foveal cones, a regular pattern ofstimulating electrodes may result in a pattern of phosphenes that iscompressed to the center of the visual field.

In order to address this case, applicants have altered the spatial mapto undo the perceptual distortion. In particular, in cases where thepatient cannot resolve the spatial information in the fine resolution ofthe spacing between electrodes, a group of electrodes are associatedwith a correspondingly large area in the video image. This is useful forcases in which areas in the array don't yield a bright percept up to themaximum allowed current. When neighboring electrodes are stimulatedsimultaneously, due to current summation, the percept is brighter.Grouping electrodes create “virtually” one electrode with a larger area,which enable to increase the maximum allowed current. As shown in FIG.5, a plurality of electrodes, e.g. four electrodes, are mapped to anaverage of a plurality of pixels, where the number of the electrodes inthe group corresponds to the number of pixels the average of which istaken. Therefore, each electrode of group (120) is mapped to a firstaverage (130) of four pixels, each electrode of group (140) is mapped toa second average (150) of four pixels, and so on.

FIG. 6 shows a further embodiment of the present disclosure, whererandom mapping is performed. For example, pixel (160), instead of beingmapped to electrode L6, is being mapped to electrode L7 (170).Similarly, pixel (180), instead of being mapped to electrode L2, isbeing mapped to electrode M8 (190). Random mapping can be used in orderto test whether a specific subject is benefitting from spatialmodulation in the array. Flexible spatial mapping can also solve wiringmistakes in the implant that are found after the implantation surgery.

A third embodiment can also be provided, which is a combination of thefirst two embodiments. In other words, a plurality of electrodes israndomly mapped to an average of a plurality of pixels.

The embodiments of FIGS. 5 and 6 have been shown with reference to a 4×4electrode arrangement for the sake of simplicity. Current electrodearrangements are in a 6×10 array (e.g., electrodes A1 through F10), andthe 6×10 electrode array represents the best mode of the presentdisclosure. The person skilled in the art will note that the embodimentsof FIGS. 5 and 6 can be easily adapted to a 6×10 electrode arrayenvironment.

Therefore, in accordance with some of the embodiments of the presentdisclosure, an improved method of operating a visual prosthesis isdisclosed. The method uses spatial maps to control neural stimulationfor correcting distortions from the foveal pit, correcting wiringmistakes in the implant, bypassing broken electrodes, testing theresolution limit, testing the benefit the patient receives from correctspatial mapping, and solving orientation problems.

Accordingly, what has been shown are methods and systems for providingstimulation inputs to a visual prosthesis implant. While these methodsand systems have been described by means of specific embodiments andapplications thereof, it is understood that numerous modifications andvariations could be made thereto by those skilled in the art withoutdeparting from the spirit and scope of the disclosure. It is thereforeto be understood that within the scope of the claims, the disclosure maybe practiced otherwise than as specifically described herein.

1. A method of mapping data to electrodes of a neural stimulator implant adapted to be positioned on neurons of a subject, the method comprising: associating a plurality of data points to form a data group; associating a plurality of electrodes to form a group of electrodes; and mapping the data group to the group of electrodes.
 2. The method of claim 1, wherein the group of data points exhibit an average data point value, and wherein the mapping of the group of data points to the group of electrodes results in configuring the neural stimulator implant to excite each electrode of the group of electrodes with the average data point value.
 3. The method of claim 1, wherein the number of data points in the group of data points is the same as the number of electrodes in the group of electrodes.
 4. The method of claim 1, wherein associating the plurality of data points and associating the plurality of electrodes are controllable associating operations.
 5. The method of claim 1, wherein a total number of electrodes is 60, arranged in a 6×10 array.
 6. A method of undoing perceptual distortion in a subject, comprising: providing the subject with a neural stimulator implant, the neural stimulator implant configured to acquire data and comprising electrodes positioned on neurons of the subject; and mapping the relationship of data points of the acquired data to the electrodes in accordance with the method of claim
 1. 7. The method of claim 6, wherein the group of data points exhibits an average data point value, and wherein mapping of the group of data points to the group of electrodes results in configuring the neural stimulator implant to excite each electrode of the group of electrodes with the average data point value.
 8. The method of claim 6, wherein the number of data points in the group of data points is the same as the number of electrodes in the group of electrodes.
 9. The method of claim 6, wherein associating the plurality of data points and associating the plurality of electrodes are controllable associating operations.
 10. A neural stimulator implant comprising: an implanted portion having a wireless receiver and an array of electrodes suitable for stimulating neurons; and an external portion having a data processing unit and including a redirection map, wherein the redirection map establishes a relationship between data acquired by the neural stimulator implant and the array of electrodes, the relationship providing an association between an average data point value of a plurality of data points and a subset of the array of electrodes.
 11. The neural stimulator implant of claim 10, wherein the plurality of data points consists of a number of data points equal to a number of electrodes in the subset of the array of electrodes.
 12. The neural stimulator implant of claim 10, wherein multiple associations between average data point values and subsets of the array of electrodes are provided.
 15. A neural stimulator implant comprising: an implanted portion having a wireless receiver and an array of electrodes suitable for stimulating neurons; and an external portion having a data processing unit and including a redirection map, wherein the redirection map establishes a relationship between data acquired by the neural stimulator implant and the array of electrodes, the relationship providing a random association between each data point value and each electrode of the array of electrodes.
 16. The neural stimulator implant of claim 15, wherein the array of electrodes is a 6×10 array of electrodes. 